An Expeditious Route to trans-Configured Tetrahydrothiophenes Enabled by Fe(OTf) -Catalyzed [3+2] Cycloaddition of Donor-Acceptor Cyclopropanes with Thionoesters.

A synthetic route to trans-configured tetrahydrothiophenes (THTs) through Fe(OTf) -promoted [3+2] cycloaddition of donor-acceptor cyclopropanes with thionoesters was developed. The cycloaddition proceeded in high yield with high diastereoselectivity, affording transient α-alkoxy THTs. Not only aromatic and aliphatic thionoesters, but also thionolactone were applicable to the present iron catalysis. Further transformation of the S,O-ketal functionality of the product was achieved in a highly trans diastereoselective manner. Moreover, the utility of our methodology was clearly demonstrated by the synthesis of enantioenriched trans-configured THTs.